Mils, thou or mm?

[nitro2k01]

Since we're using a base-10 counting system, it makes sense to base our measurements on powers of 10, not a mix of multiples of 7, 24 and whatever else imperial/customary entails. That's why miles is used for distances, and kfeet is used for altitudes. And that's why "mils" are thankfully used, instead of picas and points. Instead that unit introduced an ambiguity between different fields of work. Then look at the relationships between length, area, volume and mass in the two systems.

Metric is like a puzzle where all the pieces fit, and imperial/customary is like fitting a square peg into a round hole.

[jmaja]

Chemistry I'm sure is almost entirely metric.

Are they? It seems they decided to go metric in 1977 "AIChe goes metric": http://www.readcube.com/articles/10.1002%2Faic.690270102
I had a presentation in AIChe meeting about ten years ago. Every paper had to use SI units, BUT use 8.5"x11" paper size, which I found very amusing under title "AIChe goes metric". I think 90+% of the presentation were given using Imperial units although the papers were in SI.

Also the chemical handbooks I have are based on Imperial units, which makes them very difficult to use, since you must use several conversion in a row.

I have extremely hard to understand why would anybody want to continue with Imperial units, which are so difficult to use and prone to errors in science and engineering.

Even the very basic engineering equations like F=ma becomes difficult with Imperial units and it gets much worse when you have powers in equations. This is all due to totally rotten system for representing different scales (e.g. inches, feets, yards and miles vs. mm, m and km).

[xrunner]

So I guess all that leaves is electronics and carpentry.

Carpentry doesn't bother anyone outside the US unless we're flying houses overseas.  But also with carpentry you have to interface a lot with existing hardware and standards.  A wall plate for a switch has been pretty much the same for the last 40 years at least

LOL - can you imagine going into Home Depot and asking for the 5.1 x 10.16 mm studs (2 x 4s). 

Just doesn't have the same ring to it.

P.S.: A 2 x 4 isn't 2 x 4 inches anyway ...

[8086]

It's not hard to figure out units when talking in context.

If we're talking PCBs, 1 mil is different enough to 1mm that you can usually work out which one someone means, even if they continually switch between them and call them both mils.

Thou is just the same as mil. But I haven't encountered anyone using it IRL.

I generally use mm for everything.

[Neilm]

I tend to use mm for board design at work as I have to worry about clearances to meet international standards and these are all worked out in mm.

[deth502]

P.S.: A 2 x 4 isn't 2 x 4 inches anyway ...

it is, actually. thats why they call it a 2x4. when they rough cut lumber it is 2"x 4". then it is kiln dried, which shrinks it a little. if you buy a kiln dried 2x4 from a sawmill, your going to get something right around 2"x4" +0/-1/8". the lumber is then processes, planed down, corners rounded, and shipped to your home depot. after planing them smooth they are approx 1 1/2" x 3 1/2". when you work with rough cut lumber you will learn that 2x4's are 2x4, 1x is 1", and 5/4 is 5/4"

now, when i hear "mils" i think milradians, so fuck all 'a yall.

[rolycat]

LOL - can you imagine going into Home Depot and asking for the 5.1 x 10.16 mm studs (2 x 4s). 

You'd get very funny looks in any country if you asked for 5.1 x 10.16 mm studs. That would be 0.2 by 0.4 inches.

P.S.: A 2 x 4 isn't 2 x 4 inches anyway ...

Indeed. However, if you're buying studwork timber in a country like the UK you would likely ask for 38 x 89 mm, which is 38 x 89 millimetres.
You might very well pronounce 'mm' as 'mil'...

When most people buy timber they don't really care what it looked like when being rough cut in the sawmill 

[xrunner]

You'd get very funny looks in any country if you asked for 5.1 x 10.16 mm studs. That would be 0.2 by 0.4 inches.

LOL, yea didn't have enough coffee this morning. 

[KerryW]

LOL - can you imagine going into Home Depot and asking for the 5.1 x 10.16 mm studs (2 x 4s).

Are you building a doll house? (a 2x4 is ~5x10 CM, not MM)

Both systems are arbitrary, and whether you are talking .472" or 4.72mm, you need to measure using appropriate instruments.

The scaling argument doesn't carry much weight, either.  I have never had to measure mile distances to the inch, or kilometer distances to the mm.  But I have a calculator, should I ever need to.

It can be frustrating to compare, for example, two motors, one with torque listed in oz-in and the other in N-cm.  How hard is it to provide both on a spec sheet?

On the other hand, current flow is NOT arbitrary.  Electrons are what is flowing, and they flow from negative to positive.  They go from the emitter to the collector, NOT from the collector to the emitter.  They go from the source to the drain.  Now, how many people who think I should trade one arbitrary system for another would be willing to trade their demonstrably incorrect system ("current flow") for a correct one?  (I learned electron flow in the US NAVY)

[c4757p]

P.S.: A 2 x 4 isn't 2 x 4 inches anyway ...

it is, actually. thats why they call it a 2x4. when they rough cut lumber it is 2"x 4". then it is kiln dried, which shrinks it a little. if you buy a kiln dried 2x4 from a sawmill, your going to get something right around 2"x4" +0/-1/8". the lumber is then processes, planed down, corners rounded, and shipped to your home depot. after planing them smooth they are approx 1 1/2" x 3 1/2". when you work with rough cut lumber you will learn that 2x4's are 2x4, 1x is 1", and 5/4 is 5/4"

When I buy a pound of flour at the grocery store, I'm not the least bit interested in how much the raw wheat weighed.

[free_electron]

LOL - can you imagine going into Home Depot and asking for the 5.1 x 10.16 mm studs (2 x 4s). 

Just doesn't have the same ring to it.

P.S.: A 2 x 4 isn't 2 x 4 inches anyway ...

I found that out a couple of years ago. I asked what the common lumber size were. 2x4 4x4 etc. i worked out my exact dimensions thinking "this is easy, it's all standardized."
I come home and nothing fits. WTF ? So i doublecheck. Go back to store andco plain about them giving me wrong stuff. I asked 2x4 and its clearly waaaaay off. Answer: no it is correct 2x4 doesnt mean 2 inch by 4 inch

Ghaaaaaa !

[minime72706]

This thread exploded a bit, but what I have to say about people who bitch about the US continuing to use the Imperial system is that it would be unimaginably expensive to retrain people and retool machines. Through that process I bet you cash money that mistakes will be made and both money and lives will be lost. I wish we'd convert as much as anyone, but I just don't see it happening. It sucks ...

[rolycat]

This thread exploded a bit, but what I have to say about people who bitch about the US continuing to use the Imperial system is that it would be unimaginably expensive to retrain people and retool machines. Through that process I bet you cash money that mistakes will be made and both money and lives will be lost.

It really wouldn't. Pretty well every other country in the world has managed it without going bust or killing half their citizens. As was alluded to above, the UK largely soft-converted its building industry, so nominal 2 x 4 timber became 38 x 89 mm and half-inch plasterboard (drywall) became 13mm without any actual changes in their dimensions.

The only reason the US has gotten away with it until now is that you are relatively isolated and insular, and you are/were big enough to force countries importing US goods to accept your non-standard standards in a number of industries.

The British Empire did much the same thing while it had the power - heck, why do you think they are called Imperial measurements?

[MrsR]

Back in the early 1980s we designed an aircraft.
Now being good law abiding Australians (the Gov. made it law that only Metric could be used ) we struggled and learned Metric and sent the Aerodynamic and structural calculations with the drawings all in Metric into CASA. A short time later the package came back with a query "WHAT THE HELL IS THIS RUBBISH" do it in Imperial and re-send. The reason for this is that a decimal point in the wrong place is easy to miss in metric and can change an amount by 10, 100, 1000 or even a million. newton load over a sq. meter or was that 1 newton per sq. mm.

As for measurements for Engineering drawings Mills means metric and thou. is imperial and I much prefer thou on my drawings than parts of MM.
When using CAD we use decimal and put Millimeters or Imperial and can put a denominator .1520" or .1520MM   NOTE: When I wrote .1520" Google came on screen with 3.8608

I'm around the twist already??? Rachael

[KerryW]

This thread exploded a bit, but what I have to say about people who bitch about the US continuing to use the Imperial system is that it would be unimaginably expensive to retrain people and retool machines. Through that process I bet you cash money that mistakes will be made and both money and lives will be lost. I wish we'd convert as much as anyone, but I just don't see it happening. It sucks ...

I am reasonably comfortable with both systems, but I typically use inches.  My lathe/mill has inch leadscrews (20 TPI), but I built a DRO that displays inch or mm.  I have an X-Y stage with CNC steppers, but I didn't bother to add metric, as my CAD program will provide data in inches.  My dial indicators, calipers and micrometer are all in inches.

I don't think metric will become popular in this country until you can buy metric hardware  in a local hardware store.  Drills, taps, screws, nuts, etc have to be ordered.

[N2IXK]

US dimension lumber originally WAS the full nominal dimensions.  This changed somewhere in the 1920s or 1930s, when sawmills became more automated and standardized. My house was built around 1905, and all the original wall studs are a full 2" x 4", whereas a modern "2 x 4" is  ~ 1.5" x 3.5 ".  Sometimes calls for some creativity (and strips of plywood as shims) when interfacing between old and new construction.

Quite often, I do some machining of metal and plastic parts for various projects. The manual dials on the milling machine and lathe are all calibrated in thousandths of an inch.  If I have to work in metric, the digital readout that has been added to the machines can be set to read in decimal inches or mm. But the machines themselves were designed for the US standards, and most of the collets, tooling, and stock we work with is also manufactured in imperial sizes.

This was probably the real reason for the reluctance to convert completely to metric here in the US. Perfectly serviceable capital equipment would need to be scrapped, entire supply chains retooled, etc. A huge expense, and a waste of perfectly usable resources, with no immediately apparent payoff. Given the tendency of businesses and politicians to not think past the next quarterly report or election cycle, the result isn't exactly a surprise.

[Bored@Work]

The reason for this is that a decimal point in the wrong place is easy to miss in metric and can change an amount by 10, 100, 1000 or even a million.

And the next argument is pulled out of the arse. Easy to miss wrong decimal points in metric? You imperial fanatics know no shame. As if a wrong decimal point has no effect in imperial rubbish.

This was probably the real reason for the reluctance to convert completely to metric here in the US. Perfectly serviceable capital equipment would need to be scrapped, entire supply chains retooled, etc. A huge expense, and a waste of perfectly usable resources, with no immediately apparent payoff.

And the next one ...  Nothing has to change, nothing retooled, except that you start with new stickers to put on your wares, providing information in metric units.

[Rufus]

Seriously, I find this "imperial is easier to divide", precision and other "arguments" hilarious every time they are brought up. People are coming up with them not recognizing that the numbers they use in their "proofs" are always fudged.

The only reason we use a decimal system is we evolved with 10 fingers.

Decimal lets you easily halve and fifth, Duodecimal lets you easily halve, third, quarter, and sixth.

If we could start over again and choose a number base for general use it would be duodecimal or possibly hex.

[WBB]

LOL - can you imagine going into Home Depot and asking for the 5.1 x 10.16 mm studs (2 x 4s). 

Just doesn't have the same ring to it.

P.S.: A 2 x 4 isn't 2 x 4 inches anyway ...

I found that out a couple of years ago. I asked what the common lumber size were. 2x4 4x4 etc. i worked out my exact dimensions thinking "this is easy, it's all standardized."
I come home and nothing fits. WTF ? So i doublecheck. Go back to store andco plain about them giving me wrong stuff. I asked 2x4 and its clearly waaaaay off. Answer: no it is correct 2x4 doesnt mean 2 inch by 4 inch

Ghaaaaaa !

It wasn't a 2 x 4 when it was growing in the forest and it isn't when you buy it. But at some point in between it was in the neighborhood of 2" x 4" so that's what we get. Granted it's simpler to say than the actual dimensions and we all know that 2 x 4s aren't really 2" x 4". The problem is that before we all knew this information each of us had to learn it. Some had an easier and cheaper lesson than others.

Back on topic. For a lot of the things the average person needs to physically measure, a millimeter provides adequate resolution. Obviously that doesn't apply to everyone but is more than enough for many of us. If I want to measure an opening in an enclosure, an enclosure, or even lumber, millimeter resolution is often more than adequate. To measure an enclosure, or an opening in said enclosure, I can use a cheap ruler than often has both inch and metric markings. I can choose to have my whole number resolution be either 1" or 1mm. I'll take the latter.

I am definitely in the camp that wishes the US would switch. I agree that it would be expensive but I'm not so sure it would be as expensive as we might think. Most manufacturing equipment is computer controlled and I would think those computers could handle conversions in software quite well. I realize that wouldn't work in all instances but probably would for many. It probably already happens in the reverse anyway. Changing standardized things (lumber for example) would suck for a while. But then again, just because our new 2 x 4s would likely be called 5 x 10s doesn't mean they actually have to be within a couple millimeters of those dimensions.

[WBB]

The reason for this is that a decimal point in the wrong place is easy to miss in metric and can change an amount by 10, 100, 1000 or even a million.

And the next argument is pulled out of the arse. Easy to miss wrong decimal points in metric? You imperial fanatics know no shame. As if a wrong decimal point has no effect in imperial rubbish.

At least with the metric system, a misplaced decimal point might well be a large enough error that someone would actually notice there was a error and correct it.

[Tepe]

Nothing has to change, nothing retooled, except that you start with new stickers to put on your wares, providing information in metric units.

Exactly. A 2x4 would just be a 38x89 or more likely still a 2x4. In this here metric country it is still a to fire bom (two four beam). As for weird things happening to timber sizes: here in DK a 5" board has shrunk from 13 cm to 12.5 cm because of a switch from tommer to inches.

[MrsR]

The reason for this is that a decimal point in the wrong place is easy to miss in metric and can change an amount by 10, 100, 1000 or even a million.

And the next argument is pulled out of the arse. Easy to miss wrong decimal points in metric? You imperial fanatics know no shame. As if a wrong decimal point has no effect in imperial rubbish.

This was probably the real reason for the reluctance to convert completely to metric here in the US. Perfectly serviceable capital equipment would need to be scrapped, entire supply chains retooled, etc. A huge expense, and a waste of perfectly usable resources, with no immediately apparent payoff.

And the next one ...  Nothing has to change, nothing retooled, except that you start with new stickers to put on your wares, providing information in metric units.

HOPE YOUR REAR END IS HURTING.

You can not just put new metric stickers on all the lead screws etc would have to be changed.
Work it out.

Rachael

[jmaja]

When using CAD we use decimal and put Millimeters or Imperial and can put a denominator .1520" or .1520MM   N

That is completely wrong! M is used for "mega", which means 1e6 and meter is not M it is m. Mm=1e9*mm and MM is nothing in SI units. The same prefixes are used for every unit and this is what makes the SI system so easy to use.

[MatCat]

Everyone who is arguing needs to watch this!



Now as an American, I find myself using both systems about equally.

[tszaboo]

This thread exploded a bit, but what I have to say about people who bitch about the US continuing to use the Imperial system is that it would be unimaginably expensive to retrain people and retool machines. Through that process I bet you cash money that mistakes will be made and both money and lives will be lost. I wish we'd convert as much as anyone, but I just don't see it happening. It sucks ...

Yes, it is easyer to convince people to make another war to boost economy than convince them to use a different UoM just to be compatible with the other 200 +/- 5 countries in the world.
All in favor  the imperial system: please give us the equivalent to: weber, tesla, oersted.
Also, express the boltzmann's constant or the average distance between C atoms in the diamond in the imperial system.